1. Field of the Invention
The present invention relates to reamers, and, more particularly, to acetabular reamers, patella reamers and glenoid reamers, cutting edges on such reamers and methods of making the cutting edges.
2. Description of the Related Art
Reamers are used by surgeons to prepare bones for receiving components of artificial joints. An acetabular reamer is used to cut a cavity into the pelvic bone into which the socket portion of an artificial hip joint can be inserted. Patella reamers are used to shape the patella in knee operations. Glenoid reamers are used to prepare shoulder sockets for insertion of artificial shoulder joints. The dimensions and shape of the cavity cut are critical in many such operations, as the tolerances between the cavity and the socket portion of a joint must be small to ensure proper function. This is especially true with the newly available xe2x80x9ccementlessxe2x80x9d prostheses. In xe2x80x9ccementlessxe2x80x9d prostheses, the socket portion is frictionally fit into a cavity, placing added importance upon accurate cavity dimensions and tolerances.
Known methods of making reamers include forming holes in the reamers, from which a peripheral portion of the hole subsequently forms a cutting edge that is sharpened. Circular holes have been used, with the cutting edge being a curved portion of the periphery of the hole. Partly circular holes also have been used, in which the cutting edge is defined by a chord of the circle. xe2x80x9cDxe2x80x9d shaped holes are also known. Still other known shapes for the holes are based upon closed geometric shapes other than circles, such as ellipsoids. In these versions, the cutting edge is straight in the plane of the hole, with the cutting edge being both formed into the shape desired, and later sharpened. The cutting edges, however, in many situations cannot be shaped optimally, in that the opposite ends of the cutting edge are attached to the periphery of the hole. Thus, forming the cutting edge into any shape whatsoever naturally involves portions of the hole periphery, or portions of the cutting edge that are angular with other portions of the cutting edge both in planes generally parallel to and generally perpendicular to the reamer surface. It is therefore highly desirable to provide a new and improved reamer cutting edge, and method for making the same, by which the cutting edge may be shaped as desired. It is also highly desirable to provide a new and improved cutting edge for reamers by which more accurate cavity dimensions and smaller tolerances can be maintained, and a new improved method for making the same.
The cutting edges in reamers desirably have a long useful life. The shape of the cutting edge can influence both the useful life of the cutting and the ease by which it cuts. Thus, it is highly desirable to provide a new and improved reamer having cutting edges the shape of which is less limited by the structure of the reamer. It is also highly desirable to provide a new and improved reamer in which the cutting edge can be made to cut in shear. It is also highly desirable to provide a new and improved reamer with optimally shaped cutting edges.
In most operations in which surgical reamers are used, desirably, the bone chips cut by the reamer are saved, to be used during the operation to fill voids between the prosthesis and the hole formed by the reamer. It is known to save the bone chips within the reamer. Therefore, it is highly desirable to provide a new and improved reamer construction having means for saving the bone chips during an operation in which the reamer is used.
Reamers that are designed for repeated use require sterilization. Therefore, it is highly desirable to provide new and improved reamers which can be stripped in the field and sterilized for re-use, and which do not have crevices and other structure to hold bone chips and tissue from the operation which cannot be easily dislodged prior to sterilization.
Finally, it is highly desirable to provide a new and improved reamer construction and cutting edges therefore, and a method for making the same, which possess all of the above desired features.
It is an advantage of the invention to provide a new and improved reamer cutting edge, and a method for making the same, by which the cutting edge may be shaped as desired.
It is also an advantage of the invention to provide a new and improved cutting edge for reamers by which more accurate cavity dimensions and smaller tolerances can be maintained, and a new and improved method for making the same.
It is also an advantage of the invention to provide a new and improved reamer having cutting edges the shape of which is less limited by the structure of the reamer.
It is also an advantage of the invention to provide a new and improved reamer in which the cutting edge can be made to cut in shear.
It is also an advantage of the invention to provide a new and improved reamer with optimally shaped cutting edges.
It is also an advantage of the invention to provide a new and improved reamer construction having means for saving the bone chips during an operation in which the reamer is used.
It is also an advantage of the invention to provide a new and improved reamer that can be stripped in the filed and sterilized for re-use, and which does not have crevices and other structures to hold bone chips and tissue which cannot be easily dislodged prior to sterilization.
It is also an advantage of the invention to provide a new and improved reamer construction, cutting edges therefore, and a method for making the same which possess all of the above desired features.
In the broader aspect of the invention, there is provided a new and improved reamer having a plurality of openings therein. Each of the openings has a periphery and a cutting edge selected from the periphery. Opposite portions of the periphery are extended past the cutting edge, in a direction opposite to the direction of the opening, and transversely of the cutting edge, thereby forming spaced apart relief slots, whereby the cutting edge may be shaped as desired independently of the shape of the periphery.